Problem: $-7rst + s + 2t - 1 = -5s - 4t - 4$ Solve for $r$.
Answer: Combine constant terms on the right. $-7rst + s + 2t - {1} = -5s - 4t - {4}$ $-7rst + s + 2t = -5s - 4t - {3}$ Combine $t$ terms on the right. $-7rst + s + {2t} = -5s - {4t} - 3$ $-7rst + s = -5s - {6t} - 3$ Combine $s$ terms on the right. $-7rst + {s} = -{5s} - 6t - 3$ $-7rst = -{6s} - 6t - 3$ Isolate $r$ $-{7}r{st} = -6s - 6t - 3$ $r = \dfrac{ -6s - 6t - 3 }{ -{7st} }$ Swap the signs so the denominator isn't negative. $r = \dfrac{ {6}s + {6}t + {3} }{ {7st} }$